Liquid crystal displays are commonly used as display devices for compact electronic apparatuses, because they not only provide good quality images but are also very thin. Because liquid crystal in a liquid crystal display does not emit any light itself, the liquid crystal requires a light source to clearly and sharply display text and images. Therefore, a typical liquid crystal display requires an accompanying backlight module.
Referring to FIG. 11, a typical backlight module 9 includes a first diffusing film 91, a first brightness enhancement film (BEF) 92, a second BEF 93, a second diffusing film 94, a light guide plate 95, a reflective film 96, and a light source 97. The first diffusing film 91, the first BEF 92, the second BEF 93, the second diffusing film 94, the light guide plate 95, and the reflective film 96 are arranged in that order from top to bottom. The light guide plate 95 includes a light incident surface (not labeled) adjacent to the light source 97, a bottom surface 952 adjacent to the reflective film 96, and a light emitting surface 954 adjacent to the second diffusing film 94.
In operation, most light beams emitting from the light source 97 are transmitted into the light guide plate 95, and are converted by the light guide plate 95 to a surface light source. The second BEF 93 and the first BEF 92 cooperate to enhance a brightness of the light beams output from the light guide plate 95. However, the need for the first BEF 92 and the second BEF 93 generally adds to the cost of the backlight module 9, and makes the backlight module 9 somewhat thick. Moreover, in assembly of the backlight module 9, a step of aligning and attaching the first BEF 92 and the second BEF 93 is needed. The step is typically performed by manual labor, and adds to the cost of manufacturing the backlight module 9.
What is needed, therefore, is a backlight module that can overcome the above-described deficiencies. What is also needed is a liquid crystal display employing such a backlight module.